Photosensitive Transistor Array for Pen Tablet Signal Detection
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Solution Overview
Problem
Conventional optoelectronic pen tablets suffer from reduced aspect ratio and dynamic range due to the need for capacitors to store optical signals, which also store background light-generated charges, leading to interference and limited sensitivity.
Innovation Solution
A photo detector unit integrated into a thin-film transistor layer of a liquid crystal display panel, featuring an array of photosensitive transistors and amplifier modules that convert optical signals into currents, with adjustable resistors to cancel background currents and amplify image currents, thereby enhancing sensitivity and dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If capacitors are used to store optical signals in conventional optoelectronic pen tablets, then optical signals can be stored and converted into electrical charges, but the aspect ratio of the panel is reduced and the dynamic range is narrowed due to additional area requirements and background light interference
Solution Approach 1:
The patent removes the capacitor component from the detector array entirely, replacing the conventional store-then-convert approach with a direct convert-then-subtract approach. Photosensitive transistors convert optical signals directly to electrical currents, which are then processed to eliminate background light effects, eliminating the area consumption and aspect ratio reduction caused by capacitors
Solution Approach 2:
The patent replaces the electrical storage mechanism (capacitors) with a direct photoelectric conversion and signal processing mechanism. Instead of storing charges in capacitors and later reading them, the system directly converts optical signals to currents through photosensitive transistors and uses signal processing to achieve the same functional outcome without the intermediate storage step
2Reliability
If capacitors are used to store optical signals, then signal storage is achieved, but background light-generated charges are equally stored, resulting in a relatively narrow dynamic range
Solution Approach 1:
The patent applies preliminary anti-action by introducing a reference detector array that simultaneously measures background light and actively subtracts it from the signal detectors' output. This pre-compensation approach eliminates background light interference before it can affect the dynamic range, allowing the system to maintain high sensitivity across a wider range of signal intensities
Solution Approach 2:
The patent introduces a reference detector array as an intermediary element that measures background light levels and provides compensation signals to the main detector array. This intermediary system enables the main detectors to operate with extended dynamic range by continuously canceling out background light effects through active subtraction
3Reliability
If additional capacitors are added to the detector array, then signal storage is improved, but device complexity and area consumption increase
Solution Approach 1:
The patent extracts and removes the capacitor component from the detector array structure, replacing the multi-component store-convert-read architecture with a simplified convert-process-output architecture using photosensitive transistors and signal processing circuits
Solution Approach 2:
The patent makes the conductive lines serve multiple functions: they act as both gate lines for controlling the photosensitive transistors and as signal readout lines. This multi-functionality eliminates the need for separate storage capacitors and associated control circuitry, reducing overall device complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively minimizes background light interference, expands the dynamic range, and maintains a stable output signal, allowing for accurate detection of input signals from styluses, pens, and shadows with improved sensitivity and area efficiency.
Implementation Method 1
each photosensitive transistor... capable of detecting an optical signal including an image component and a background component, and converting the optical signal into a current including an image current corresponding to the image component and a background current corresponding to the background component
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A photo detector device includes a photosensitive transistor (14-1) capable of detecting an optical signal including an image component and a background component and converting the optical signal into a current including an image current (IM) corresponding to the image component and a background current (IB) corresponding to the background component, a first amplifier module (11) electrically connected to the photosensitive transistor capable of canceling the background current and amplifying the image current, and a second amplifier module (12) electrically connected to the first amplifier module capable of detecting a direct-current (dc) portion of the image current.